This application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2004-0101534, filed on Dec. 4, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to equalizers, decoders, receivers, and methods for the same.
2. Description of the Conventional Art
Broadcasting systems may utilize OFDM (Orthogonal Frequency Division Multiplexing) based DVB-T (Terrestrial Digital Video Broadcasting) or VSB (Vestigial Sideband Broadcasting), for example, as defined by the ATSC (Advanced Television Subcommittee). A VSB digital television receiver may utilize a more robust receiver capable of receiving a VSB signal including inter-symbol interference through a multi-path channel, more stably demodulating, and/or more stably decoding the received VSB signal.
FIG. 1 is a block diagram of a conventional digital television receiver 100, which may process a VSB signal. Referring to FIG. 1, the digital television receiver 100 includes a tuner 110, a demodulator 120, an equalizer 130, and a TCM (Trellis-coded Modulation) decoder 140. TCM coding may use an error correction technique, which may improve system robustness against thermal noise. TCM decoding may have more robust performance ability and/or a simpler decoding algorithm. The output signal OUT of the TCM decoder 140 may be processed by a signal processor and output as multimedia signals (e.g., display signals and/or audio signals).
FIG. 2 illustrates an example of a conventional decision-feedback equalizer (DFE) 200, which may be used as the equalizer 130 of FIG. 1. Referring to FIG. 2, the DFE 200 includes a feed-forward filter 210, an adder 220, a slicer 230, and a feedback filter 240. The DFE 200 may receive the output signal of the demodulator 110 of FIG. 1 as an input signal INPUT, equalize distortion of the received signal and output the equalized signal to the TCM decoder 140 of FIG. 1. The DFE 200 may be positioned, for example, prior to the TCM decoder and may use uncoded symbols to perform a feedback process. However, the uncoded symbols may have lower reliability.
FIG. 3 illustrates a conventional digital television receiver 300 having a DFE 310 combined with a TCM decoder 320. Referring to FIG. 3, the DFE 310 may include a feed-forward filter 311, an adder 312, a slicer 313, and a feedback filter 314. The TCM decoder 320 may decode the output signal EQO of the DFE 310, and may generate symbol decisions H1, H2, H3, . . . , using a branch metric computation and traceback procedure that may be the reverse of the TCM encoding process. The symbol decisions H1, H2, H3, . . . , which may be fed back to the feedback filter 314, may have higher reliability because they may be generated from a more (e.g., the most) probable surviving path.
However, the TCM decoder 320 generating the symbol decisions H1, H2, H3, . . . , may utilize a higher system clock rate to operate with suppressed (e.g., without) delay, which may increase hardware complexity and/or power consumption. In the alternative, a more hardware efficient TCM decoder 320 may introduce delays in the decoding process. For example, the first available decision from TCM decoder 320 (H1) may be delayed by D symbols, where D may be, for example, 2 to 7 symbols. To suppress performance degradation, a first D taps of the feedback filter 314 may be filled with decisions produced by the slicer 313. The remaining taps may be filled with the symbol decisions H1, H2, H3, . . . produced by TCM decoder 320.
A transmitting device transmitting a VSB signal may include a TCM encoder 400 shown in FIG. 4. Referring to FIG. 4, the TCM encoding device 400 used in a broadcasting system (e.g., an ATSC broadcasting system) includes a first switch 410, twelve parallel TCM encoders 420, 430 and 440, and a second switch 450. The first TCM encoder 420 may TCM-encode a first symbol group of input data, for example, the first, thirteenth and twenty-fifth symbols. The second TCM encoder 430 may TCM-encode a second symbol group of the input data, for example, the second, fourteenth and twenty-sixth symbols. The twelfth TCM encoder 440 may TCM-encode a twelfth symbol group of the input data, for example, the twelfth, twenty-fourth and thirty-sixth symbols. This code interleaving operation of the TCM encoding device 400 may generate a twelve symbol interval between output data items.
The TCM decoder 320 of FIG. 3 may have the same, or substantially the same, configuration as illustrated in FIG. 5. Referring to FIG. 5, the TCM decoder 320 used in the broadcasting system includes a first switch 321, twelve parallel TCM decoders 322, 323 and 324, and a second switch 325. The TCM decoders 322, 323 and 324 may each perform the branch metric computation and traceback procedure to generate symbol decisions H1, H2, H3, . . . , from a more (e.g., the most) probable surviving path. There may be a twelve symbol interval between adjacent symbol decisions.